Colt AR15 SP1 cycling issues

[Robbs]

I took a Colt AR15 SP1 out to the range the other day to try it out. The rifle was in exceptionally clean condition. Chambered the first round fine but after the first shot the rifle would not load the next round in the mag. The bolt carrier seems to slip off the next round in the mag overriding it and then stopping. I had to pull back on the charging handle ever time to chamber the next round. I tried several different types of mags including new stainless steel ones and that does not make a difference. Gas key is tight and clean as with the rest of the bolt, carrier and return spring. I compared the bolt carrier with a relatively new AR bolt carrier that works well and I cannot see any difference in terms of any wear.
I would appreciate any advice from more experienced AR owners as to what my problems might be. Thanks!

 

[smak_daddy]

Hmm. Tough one.

Sounds like it isn't a mag issue.

I know you checked the gas system but thats where my bet would be.

 

[Stevo]

What kind of ammo? Did you try a different type?

 

[Clobbersauras]

What Stevo said.

What's the barrel length? Have you inspected the buffer, receiver extension, and gas tube? Is the gas block tight?

 

[MasterMC]

Pictures please.
We could be able to see how the ammo jams while chambering and find out what causes the problem.

 

[Quiet]

Were the gaps in the gas rings lined up on the bolt. That would do it for sure.

 

[shredder]

Oh yeah, a major short-stroke problem.

First (and usually the most common cause) is the gaps on the gas rings on the bolts have lined up.

What that does is allow the gas to go straight into the upper without pushing back the bolt and bolt carrier. Take the bolt out and look at the rings. If they've lined up, that's likely the problem.

Another (less common) cause can be the ammo that's been used. It sounds like this rifle is new to you (used) and sometimes the gas tube from the gas block back to the upper is plugged from carbon residue.

 

[Robbs]

Thanks for the advice. If the gas rings on the bolt have lined up, how does one un-line them?

 

[m39a2]

Don't believe everything you read. Gas rings? Really? Not likely.
1.Have you changed anyting on the rifle since the last time you fired it? Butt stock? Bolt that holds the butt stock on?
2. Will the rifle "Lock open" when you fire the last round? Can you manually lock open the bolt by pulling the charging handle all the way back and hand operating the bolt catch? When you do, does it lock on the front of the bolt carrier behind the bolt head, or on the front of the bolt itself?
3. What weight of bullet were you using?
4. Does the empty case eject cleanly?

Scott

 

[mudgunner49]

Were the gaps in the gas rings lined up on the bolt. That would do it for sure.

No - no it would not . The AR FOW will run with one lone solitary gas ring in place. People need to start killing these stupid rumours.

Check that the gas tube is pinned properly in place at the gas block and that the gas port is not partially obstructed by the block being out of position somehow...

 

[browningautorifle]

I still think it's a mag issue. Try loading a mag and rest the mag on your hand when firing. That will hold the mag up, and if it loads correctly then change the mag catch assembly.

 

[Copper]

Ar15

I had what seems to be the same problem with my .308. Fire first round maybe second then the bolt would jam up on the next round. My solution was that I bought Pmags problem solved for me. Oh and that was after I tried all else.

 

[Farmboy]

What kind of ammo?

 

[Quiet]

Thanks for the advice. If the gas rings on the bolt have lined up, how does one un-line them?

You just use your fingernail to turn them so that the gaps are staggered. This used to be taught as a standard thing to check before re-assembly of the C7 bolt after cleaning.

 

[Dsiwy]

You just use your fingernail to turn them so that the gaps are staggered. This used to be taught as a standard thing to check before re-assembly of the C7 bolt after cleaning.

Thats half BS "army urban legend"

If there worn out yes but if there servicable then it will not matter.

You should change your gas rings though and try that "there cheap anyways "

 

[Copper]

Sp1

Well yesterday I took out my 66 SP1 to the range 1 /12 twist. ammo was 55fmj american eagle. I used 4 different mags. All but one mag worked. The mag was a Kay mag it malfunctioned as yours did.It only fired the first round before it short stroked. All the rest were loaded max even the RRA. I continued to pound out the ammo till I ran out.

 

[Robbs]

What kind of ammo?

S&B 55gr FMJ.
Thanks for the input. I will try some of the things suggested and see. It is a very nice retro rifle. I hope to get it working properly soon.

 

[Copper]

American Eagle or remington NOT S&B